Case-hardening apparatus.



3 SHEETS-SHEET l.

n. 822,460. PATENTED .TUNE 5, 1906. A. W. MAGHLET.

CASE HARDENING APPARATUS. APPLICATION FILED IBB. 4. 1905.'

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lllll WIT/VESSES No. 322,460. P ATENVTED JUNE5, 1906.

i A. W. MAGHLET. CASE HARDENING APPARATUS.

APPLICATION FILED FEB. 4, 1905.

3 SHEETS-SHEET 2.

y PATENTED JUNE 5, 1906.

No. 822,460. A. W. MAGHLET.

OASE HARDENING APPARATUS.

APPLICATION FILED I'EB.4. 1905.

3 SHEETSSHEET 3,

mw @A .wk Am @w m\ r w or .z'kE-gm g4 cult and sometimes altogether impossible tox ADOLPH W. MACHLET, OFELIZJABETH, NEW JERSEY.

CASE-HARDENING APPARATUS.

Specification of Letters Patent.

I-atented June 5, 1906.

Application filed February 4, 1906. Serial No. 244,244.

and useful Improvements in Case-Harden-- ing Apparatus, of which the following is a specification. n

This invention relates tothe case-hardening of steel and iron articles, and partlcularly `of small articles in bulk.

Small articles or parts in large quantitiesl are commonly machined or shaped from wrought-iron or low-carbon steel in sheet,

Ywire, or bar form, these metals; owing to their lack of carbon, being relatively soft, and hence easily cut and Worked by machinetools; but owing to this softness such articles are unsuited for Wear, and accordingly it is the practice to case-harden them, usually by carburizing them to a vdepth of a few thousandthsor possibly a few hundredths of an inch, so that they retain their shapes and are given sufliciently hard exteriors for the purposes for which they are intended. Casehardening is a rapid process of cementation in which the surface of the wrought-iron or low-.carbon-,steel article is converted into steel or into a higher-carbon steel by heating the1 article inl contact with carbonous matecr1a An excessive degree of heat must=be applied for a long time in order to act through the non-conducting carbonaceous material upon the articles packed therein, and this-@dicessive heat soon destroys the .iron boxes in which the articles are usually case-hardened. In many cases also it is necessary to cool, repaclt, and. reheat the' articles in order to produce a sufficient depth of cementation."

Moreover, it is found in practice very difficarburize the articles justas deeply' as `required and no deeper. In lthe case of thin'or plate-like articles, Where it is desired that the cementation shall be very shallow or thin,`

l but still completeall over .the articles,"it is found to be practically impossible to attain u the desired result, since the carburization is almost sure to proceed too far at some portions of the article, which consequently is rendered too brittle for use, it being desired to preserve the relatively soft and tough character of the interior of case-hardened articles. No practicable way has heretofore been found for not only insuring that the carbonization shall be of even thinness all over small thin articles, but also causing such cementation to proceedto the exact depth required, so that it would be practicable to case-harden such articles.

. The principal objects of my invention'a're to materially reduce the cost of case-hardening articles, to insure that the case-hardening operation shall produce a shell of uniform thickness all-over the article regardless of its shape, to regulate or gage exactlyT the thickness of the cementation or shell, to make it practicable to case-harden small articles cheaply and rapidly and uniformly in bulk, and to provide for inexpensively and effectually tempering the case-hardened articles by sudden cooling thereof.

I heat the articles to a point above redness, but below the melting-point, in an atmosphere of carbonous gas, preferably under high pressure-say from twenty-five up to one hundred pounds,v or even more, to the -square ,inch-and preferably effect gentle agitation of the articles during the heating,

thus exposing all portions thereof to thegas,

so as to insure the uniform penetration ofthe -carbon from the gas at all points on the surface of the article, both outside and inside, and Without regard to the shape of the same. Thus I avoid the necessity and expense of rst packin thearticles in carbonaceous substances in t e usual manner. I use .a retort made, preferably, of metal, with which the articles directly contact, sothat they .are quickly heated Without unduly heating the retort, thus saving cost/of fuel and avoidin dev.te rmi'ned, and the cementation may e arrested at any point, the thickness ofthe shell being determined in'advanc, even to a thousandth art of an inch, by anoperator having fair ski l in using the apparatus. the process of cementation as 'soon as the predetermined thickness or depth is acquired,

TOO

I. arrest IIO and since case-hardened articles are usuallyY` tempered vor Inade.glasshard7 I provide means for suddenly cooling them while stilly hot-that is, before they lose the heat acappears upon fracture. I

en cooling may be effected in any approved 'manner, as by plunfging the articles into a cold liquid-bath. I this is done while the articles are still at carburizing heat-that is, above red heattheir tempering is effected, and this sort of tempering will answer for numerous kinds of articles where it is unimportant whether the shell has a coarse or fine grain. When the articles are chilled at this high heat, the shell acquires a coarse grain, as I therefore provide for gradually permitting the articles to cool from carburizing heat to cherry-red and then plun ing them into the cooling-bath, wherey W en desired'a better quality of steel may be produced. When tempered in this manner, the shell appears to have a very fine rain when fractured, and the expense and rglelay of permitting the articles to cool gradually to ordinary atmospheric heat and subsequently reheating them for tempering are avoided, and the scaling of the surface due to such-cooling and reheating is also avoided. By this means it becomes practicable to produce perfectly and evenly case-hardened finely-tempered articles which have been first shaped or machined from wrought-iron or low-carbon steel, and it is even practicable to manufacture large quantities of tools and articles and harden and temper them according to my'invention which heretofore it has been necessary to produce slowly and expensivef from fine high-carbon or tool steel. ther objects and advantages will hereinafter appear.

In the accompanying drawings, Figure l represents a sectional e evation, taken from end to end, of one formof a case-hardening and tempering apparatus constructed for case-hardening an tempering articles according to my invention. Fig. 2 .is an elevation of the left-hand end, and Fig. 3 an elevation of the right-hand end, of the carburizin apparatus seen at Fig. 1. Fig. 4 isa vertica cross-section taken near the left-hand end of theifurnace at Fig. 1. Fig. 5 is a plan, and Fig. 6 a longitudinal section, of one form'of tool used in charging the apparatus with arti- 4clesl to be carburized. Fig. 7 isa side view,

and Fig. 8 an en d view, of another formI of charging-tool. Fig. 9 is a sectional view vof an example of a case-hardened article, illustrating a thin shell formed evenly all over the same.

The steel or liron articles to lbe case-hardened are represented by a dotted line 1, deposited in bulk within al retort 2, formed of cast-iron or other suitable metal, the retort being preferably about half or two-thirds full. The retort is preferably inthe form of a barrel .or lelon ated cylinder land is mounted wholly Within a flame-chamber 3 of a furnace 4, the latter comprising a cylindrical or other bodyl 5, having heads 6 and 7. The furnace is provided throughout with a refractory lining, the cylindrical portion thereof which lines the body being indicated at 8 and that portion which lines the heads of the furnace being indicated at 9, all of said lining being usuallly set inA plaster-of-paris, (seenat 10.) The space inclosed by said refractory lining forms said flame-chamber. Any suitable fuel may be consumed in the furnace, and it may be otherwise constructed. Preferably a mixture of hydrocarbon fuel with air is used, the air being admitted through a pipe 11 and the fuel, such as ordinary illuminating or heating gas, being admitted througha ipe 12, the supply of air and fuel being regulated by valves 13 .14. The air and fuel become mixed within the pipes 15 16, and the mixture is admitted to burners 17 18, inserted in horizontal openings 19 20, formed in the opposite Walls of the furnace near the top of the flame-chamber. i

The burners point alternately in opposite directions, as seen at Fig. 4, Aso as to direct the flames across the top and down around both sides of the retort and form two sets extending along the top of the flame-chamber above said retort. Two feed-pipes 21 22, extending along the furnace, connect the burners in the sets, said pipes being supplied by the pipe 16, which extends across the top of the furnace. The gas-flames are directed upon and over the retort and play down around the same and escape through an outlet 23, formed in the bottom of the furnace at the end of the retort, whereby even heating of the latter is assured. The supports for said retort are mounted upon the exterior of the furnace-heads and consist of a pair of rolls 24, carried upon brackets 25, fixed' upon the right-hand lead 7, and a pair of rolls 26, mounted upon brackets H27, fixed upon the left-hand head 6. The retort is formed with cylindrical extensions at its end, one extension 28 resting between and supported upon p the rolls 24 and the other extenslon 29 be` ing similarly supported `upon rolls 26. It will be seen that said extensions project through openings 30, formed in the refractory lining 9, and through similar openings 1n the heads of the furnace. The urpose of supporting the retort upon the rol sis to enable it to turn during the heating thereof. A partition 31, forming the top or right-hand end of th retort, is cast between the same and the rightend extension 28, the latter being preferablyJ of the same diameter as the retort itself. f

The extension 29 is preferably of larger diameter than the retort, so as to permit the insertion and withdrawal of a cover 32, that-is tted to the left-hand lend or bottom of the retort. This cover is intended to be clamped tightly upon the retort during the process of carburization, and it is removable to permit IOO IIO

Charging and discharging the retort. A screw 33, provided with handles 34 upon the exterior of the furnace, is threaded into a yoke 35, which is xed uponA the end of extension 29 by means of bolts and nuts 35a. By turning the screw the cover may be clamped tightly upon the retort or drawn off therefrom far enough to permit the articles 1 to drop or discharge through one of several apertures 36, formed in said extension 2.9v adjoining the retort and overlying the outlet 23.

In order to charge the retort, the cover, screw, and yoke are withdrawn, the latter being formed at its ends with hooks or open slots 37, which engage said bolts 35a loosely, so that by simply turning said yoke to the left at Fig. 2 it is disengaged from the bolts and may be removed, together With the screw and cover. The extension 29 is also provided with a metal closure or head 38, having a lining of asbestos, said head 38 being fixed v to the yoke 35. This head avoids waste of heat and also prevents the handles 34 from becoming unduly hot.

During the life of the apparatus the retort is alternately heated and cooled a great many times and' in consequence gradually acquires a permanent expansion-that is, it slowly grows larger. Hence the apertures 30 in the furnace are made a little' oversize, as illustrated, to accommodate the gradual increase in .circumference of the extensions,v

and the periphery of the extension 29 is smooth, so that it may slip in axial direction -along'the rolls 26 to accommodate the permanent expansion or lengthening of the retort structure, the other extension 28 having flanges 39 to inclose the rollers 24 and prevent endwise movement of this end of the re-.

tort. The aperture 23 in the bottom of the furnace is vmade of sufficient dimension from left to rightat Fig. 1 to accommodatethe permanent lengthening of the retort, so .that the aperture 36'may still overhe said opening 23 even when such lengthening has reached a maximum.

The carburizing-gasmay be a pure hydrocarbonfalthough I have found ini practice that good results are obtained by the use of ordinarycity-gaasuch as generally supplied for illuminating and heating in thecity of Elizabeth, New Jersey. Good results .can

. also be obtained from coal-gas and from oilway; but for the sake of illustration I have as and also from carbureted hydrogen gas, 2for water-gas,) resulting from the passing of steam through a mass of incandescentarbon and subsequent admixture of hydrocarbons or other enriching substances.

"The gas which is used for cementation may be -supplied under pressure in any suitable shown a'gas receiver or tank 40 which contains gas preferably lat a pressure of one hundred Vpounds to the square inch, although a much lower or even higher pressure may'be used, or in some casesthe pressure may be just a little higher than atmospheric pressure. In other words, the pressure may vary from just sufficient to charge the retort to the high'- est that may be found practicable. ceiver. is connected to the retort by means of flexible pipe 41, provided with valve 42, and a pipe 43, the latter being in line with the axis. of retort 2. A gland is shown at 44 to accommodate the rotation of the retort, since the pipe 43 remains stationary. A yoke or bracket 45 is fixed upon the head 7 of the furnace to support the gland 46, into which -pipe 43 is threaded. The latter is provided with a cap 47, which may be removed to give access to the interior of the pipe and gland for cleaning. Threaded into the end or top 31 of the retort is a jet or sprayer 48, having nul merous apertures 49 for directing the gas in\ small jets into the retort, said sprayer 48 being connected by a pipe 49 to the gland 44. If oil-gas is used, any suitable provision may be used for converting the oil into gas and forcing it through the jet or spray 48 into the retort. The heat of the retort may be used for converting the oil into gas.

In operation the yoke 35 and cover 32 are removed and the articles 1 depositedwithin the retort 2. The yoke 35 is replaced and the nutsand bolts 35a tightened and the screw 33 revolved to clamp the cover 32 tightly against the\lower or left-hand open end` of the retort. The gas and air valves 13 14 are opened andgthe fuel mixture ignited at .the burners 17 1 8, the flames circulating in opposite directions over the top and down along the sides of the retort and then to` the IOO left along the'bottom of the retort at Fig. 1, I

nally escaping downwardly through the orifice 23 in the bottom of the furnace. valve 42 is opened, and the carburizingas passes from the tank 40 through the supp y- The y pipe 41 43 49 and into the retort, the air being forced out from the latter through a vent 50, formed in the cover 32, and having an ad- IIO justable valve or screw 51, said vent remaining slightly open throughout they operation and the as escaping therefrom igniting and constant y burning. The ames in thefurnace heat the retort until the articles therein are above red heat-say from 1,5000 to-1,800O Fahrenheit-this being safely below the melting-point and sufficiently hot to effect the cementation of the articles, which process may also be favored and hastened by reason of thev high pressure at which the gas maybe supplied tothe interior of the retort. Owing to the rapidity of the cementation, a great economy is eHectedV in fuel, since the time is materially shortened during which it is necessary to consume fuel in maintaining the heat .of the retort and other parts, while of' coursel the daily capacity of the apparatus is increased. l In order that the articles shall be expose uniformly to the action of the gas, I provide means for effecting gentle agitation thereof, such means inthis instance consisting 'of a pulley 'or wheel 52, which is connected by movement-reducing gearing to the retort, so as to rotate the latter very slowly, thereby avoiding injury of the articles therein, which frequently are of delicate construction and particularly liable to become bent, owingto their heated condition. Said gear comprises` a worm 53, fixed upon the pulley-shaft 54 and turning within a drip-pan 55 -and in mesh with a worm-wheel 56, secured by bolts 57 to the right-hand extension 28 of the retort. The rotation of the latter may be very slow indeed, as its only object is to insure that each article shall be exposed all over to the action of the as.

Durin the car onizing operation fresh gas constant y enters through the supply 41-to replace the gas which has become vitiated by the absorption of the carbon elements into the metal articles, such vitiated gas escaping through the vent 50 and there producing a constant iiame, which can be seen by the operator through the sight-hole 58, whereby he can ascertain by the color of such iame whether the gas retained in the 'retort is unduly vitiated. If so, the valve 51 may be opened a little more to permit freer escape of the' gas and a more rapid inflow of One advantage of the invention consists in the circumstance that the operator may arrest the case-hardening process as soon as the cementation has proceeded to any predetermined depth up'on the articles, it being practicable to gage such a depth to within even a few thousandths of an inch or even less, according to the skill of the operator. In doing this the operator takes note of l*the time at which the articles reach the proper heat, which he can ascertain by observing through the sight-hole 58 the color' of the body of the -retort and which can also be ascertained by reading a pyrometer 59 ,which may be inserted through an aperture 60 in the bottom of the furnace and rojects slightly into the flame-chamber. gy comparison of the readin of the pyrometer with the appearance of t e incandescent retort the operator can determine precisely when the articles have reached the'required heat for cementation vand may then'admit the gas through the supply 41, and so cause the cementation to proceed for a predetermined length of time-say one hour `or even lessaccording to the quality of thegas in the retort, the'temperature thereof, the 'grade of the articles to be case-hardened, and the depth to which it is desired to have the casehardemng proceed upon the articles. The

. operator may make andl preserve memoranda of different results obtained by the use .of different qualities of gas or different suitable for the pressures of gas upon different qualities of iron or steel, noting the depth to which the .case-hardening proceeds underl the different conditions, and from such account he may readily predeterinine at any time how deep the case-hardening shall proceed u on the particular articles being treated. "his eX- actness, which is highly desirable in many instances, is rendered possible largely because of the fact that the heat of the retort is maintained absolutely uniform throughout the process ofcementation, owing to the use of burners for burning mixed air and. fuel,

whereby the heat of the retort may be not only regulated, but rendered absolutely uniform, and thus it becomes practicable and inexpensive to produce upon -the articles v shells of even predetermined thickness all over the articles, which result it has not heretofore been found practicable to obtain with certainty and'in an inexpensive manner purposes of ordinary manufacturing.

As soon as the-cementation has proceeded to the desired depth valve 42 may be closed,

the handles 34 may be turned to open the cover 32, and the articles may drop through the o ening or chute 43 into a tempering-bath of co d water or other liquid 61. i

To facilitate the discharge of the retort, I arrange to tilt the same up at its right-hand end, so .that during the continued rotatlon thereof the articles will feed gradually down to the left-hand or bottom end and finally drop through the chute 23 into the bath 61. For this purpose I pivot or hinge the furnace at 62 upon a pair of standards 63 at the lefthand end of the apparatus and provide at the IOO right-hand end a vertical screw 64, so that by I means o f said screw the right-hand end of the furnace may be elevated or tilted, together with the retort therein. The screw 64 does not turn, but is pivoted at its up er end 66 to an ear 67, depending from the urnace, and handles 65 are provided .upon a nut 68, threaded upon sa1d screw and resting upon a washer v69, carried by a block 70, -pivoted at 7,1 to standards 72. The ivoting of the block at 71 accommodates t 1e different angular positions assumed by the screw 64 as it rises 'with the furnace.

,Assoon as the articles'are discharged from the retort the latter may be recharged without becoming cold, thus avoiding the delay and expense of reheating the same. For the purpose of rechargin the tool seen at Figs.v 5, 6 may be employe consisting of a cylindrical scoop 73, having therein a piston.74, the latter provided with a rod 75 and handle 76. The piston may be drawn to the bottom of the scqof and the latter filled with small varticles an inserted within the hot retort. v

The operator thenl holds the handle 76 stationary,"while he pulls out the scoop by virc ymeans of a handle 77, thus gently depositing A13o the articles in the retort. Another form of scoop 78 is seen at Figs. 7, 8, having a handle 79. This tool ma be filled with articles and inserted Within t e retort and then gently supply 41, and the operation proceeds as before. Very little time is occupied in charging and recharging, so that waste of fuel is minimized. Thus the furnace may be kept in constant operation,` and many charges of articles may be case-hardened ever. day with but little expense for labor and el as compared with the methods of case-hardening accepted at the present time.

While for some purposes the incandescent articles may without any cooling be dumped directly into the tempering-bath 61, still for other urposes it is desirable that the articles shall rst gradually cool until they are about cherry-red, and in order to effect such gradual cooling I partly close the valves 13 14, so that only a little gas passes through the burners 17 18, just sufficient to prevent the ingress of air u through the orifice 23, thus preventing` oxldation of the exterior walls of the retort. Only a slight pressure of gas in the furnace is necessary for the purpose, and this does not materially retard the cooling of the retort and the articles therein to the desired cherry-red heat. Thus while the articles are still heated from the carburizing process Ithey ma discharge into the cooling-bath, and the she lsthereon may receive a fine temper. During such gradual cooling of the articles in the vretort the valve 42 may be closed, lso that no further carburization may take place, or, on the other hand, the valves 13 14 may be prematurely partly closed to reduce the flow of gas into the flame-chamb er and permit the gradual cooling of the retort, and the valve 42 may beleft open, so that cementation will continue as far as it may during such gradual cooling.

The cooling apparatus seen at Fig. 1 comprises a tank 80,- Which i's provided with rollers 81 to run upon the iioor, the to of the tank being just beneaththe mout of the chute 23. Within the tank rests a sieve 82, through whose perforations 83 the liquid cir- The articles drop into this sieve, which restsupon a support .84, provided in the bottom of the tank, and as soon as the articles are chilled by the bath the sieve is lifted out, the liquid escaping therefrom through said perforations 83. The articles are then dumped from the sieve and the `latter replaced inthe tank. Any other suitable apparatus or device maybe used for chilling or f cooling the articles.

It will be seen that an 1m ortant economy is effected, because the artic es are directly in contact with the metal retort, which'is subjectto the heat ofthe flames from the burners, whereby owing to the connections of the heat through the metallic body of the retort the articles are quickl heated without the necessity of forcing t e heat through the body of non-conducting carbonaceous substance. Thus not only is fuel saved, but

the necessity is avoided of damaging the retort itself, the life of which is hence greatly prolonged.

When it is desired to renew the retort, however, it is only necessary to take out the screws 57, by which the worm-wheel 56 and the flanged roll 39 are attached thereto, and

lalso to disconnect the gland 44, whereupon the retort may be pulled directly out of the furnaceto the left at Fig. 1, a new one may be put in place, and the parts 39, 56, and -44 restored.

At Fi 9 is seen an article comprising a hollow s aft 85 and flan es 86 87, formed thereon, the entire article eing covered with a thin shell 88', which, it will be understood, is of uniform thickness, since both interior and exterior parts of the article are-accessible to the gas.

Variations may be resorted to within the scope of my invention, and portions of my improvements may be used without others.

.l Having thus described my invention, I c aim- 1. A case-hardening a paratus comprising a furnacehaving a sing e chamber in which the flames `originate, a metallic retort wholly within said chamber, and a holder for carburizing fluid connected With said retort; said furnace being provided with sup orts upon which the retort is so mounted) that the flames may envelo the retort throughout its length; the retort eing provided with a constricted regulatable vent, and also having a normally closed openin distinct from said vent and through Whic articles may be removed.; and means for effecting agitation ofthe articles in the retort during the heating thereof.

2. A case-hardening apparatus comprising a furnace havin a body and ends, and havin a refractory ining for said body and ends,

the flames orlginate, a revoluble metallic retort wholly within said chamber, a holder for carburizing fluid connected with said retort; said furnace being provided with supports upon which the retort is so mounted that the flames may envelop the retort throughout its length, and said retort being removably connected to said supports, and also having a relatively constricted vent, and an opening to permit removal of the articles,I said opening having a removable cover and means for rotating said retort.

3. A case-hardening apparatus comprising afurnace havin a body and ends, and having a refractory fining for said body and ends,

'said lining forming `a chamber in which the the case-hardened IIO fiames originate, a metallic retort wholly! 4Within said chamber and having supporting extensions which protrude through said ends, said furnace having exterior supports upon which said extensions are mounted in such a manner that the retort is removable. from the furnace, and a holder for earburizing fluid connected to one end of said retort; a cover. and a constricted vent being provided at the other end of said retort.

4. A case-hardening apparatus comprising a furnace provided with a refractory lining, a. metallic retort mounted Wholly Within said lining, numerous burners for mixed air and fuel, said burners forming a set extending the entire length of the retort in such a manner as to cause the retort to be heated throughout with evenness independent of the heat of said refractory lining; means being provided for subjecting the articles in the retort to a constant current ofI carburizing-gas during the heating of the retort and means for effecting rotation of said retort.

5. A case-hardening apparatus comprising a furnace having a body and ends and provided with a refractory lining for said body and ends, a metallic retort Within said lining and having extensions which protrude through said ends, a holder for carburizing fluid connected to said retort at one end, a cover for the other end of said retort, and a manually-operable device extending without said furnace for clamping said cover, said clamping device being connected to `a head which is mounted exteriorly of said furnace, and which is detachable so that the cover, clamping device and head may be removed from the furnace While the retort remains therein 5 said retort provided with la constricted vent.

6. A case-hardening a a furnace having a sing e fire-chamber prol vided with a refractory lining, a metallic retort within said fire-chamber, a holder for carburizing fluid connected with said retort, and numerous burners for mixed air and fuel 3 said burners being directed alternately in opposite directions and forming a series extend- 1n along said retort and placed at such inter- Valls as to effect substantially uniform heating of the retort throughout its length, and the retort being so'sustained in said firechamber that the fiames may play freely around the top, sides and bottom of *the retort, and the latter being provided with a constricted vent.

7. A case-hardening apparatus comprising a furnace having a refractory lining which forms a single fire-chamber, a metallic' retort Wholly within said fire-chamber, supporting means providedupon the exterior of said furnace for said retort, the latter being removable from said supporting means, numerous burners for mixed air and fuel within said paratus comprising fire-chamber, said retort being supported in such a manner that the flames from said.

and revoluble upon supports Which are provided upon the exterior of the furnace, said retort being removably mounted at its-ends upon said sup orts, a set of burners for mixed air and nel within said flame-chamber, the walls of the latter cooperating with said burners to direct the flames with substantial uniformity beneath and around said retort, and a holder for carburizing fluid connected to said retort constricted means being provided for venting vitiated gas from the retort.

9. A case-hardening apparatus comprising a furnace having a flame-chamber, a retort mounted wholly Within said name-chamber,

a holder for carburizing fluid connected to said retort, and power-driven means for effecting agitation of the articles Within the retort during the heating thereof; means being provided for securin circulation'of the carburizing fluid Within t e retort during the heating thereof.

10. A case-hardening apparatus comprising a furnace having a flame-chamber, a retort Wholly Within said name-chamber, supports exterior to said furnace upon which said' retort is mounted for movement, a holder for carburizing fluid connected to said retort so as to supply fluid thereto durin r ment of the retort, and means f movement of the retort throughout the carburizing operation; said retort provided with a constricted vent.

' 11. A case-hardening apparatus comprising a furnace having a flame-chamber, a methe movel or effecting I'IO IOO

tallic retort Wholly Within said chamber, said f furnace provided with exterior supports engaged by means extending from said retort, and permitting rotation of the retort, and a holder for carburizing-gas connected to the retort so as to supply the same with carburizing fluid during the rotation of the retort means being provided for permitting gradual venting of vitiated gas from the retort during the carburizing operation.

12. A case-hardening apparatus compris'- ing a furnace having a single flame-chamber,

a set of numerous burners for mixed air and fuel within said flame-chamber, a retort in the form of a barrel Within said flame-chamber, said retort provided with extensions and said furnace having exterior means to engage said .extensions so as to permit rotation of the retort, and a space being left Within said name-chamber all around the top, sides and bottom of said retort for the circulation of flames, and a holder for carburizing fluid connected to said retort so as to supply the same with carburizing fiuid during the rotation of the retort; the latter provided with a constricted vent.

13L A case-hardening apparatus comprising a furnace, a closed metallic retort in the sides and bottom; said retort being pro- 4- .vided With a constricted vent.

14. A case-hardening apparatus comprising .a furnace having a flame-chamber, a metallic retort in sai chamber, means being provided for revolubly supporting said retort during the heating thereof, and a holder for carburizing fiuid connected to said retort so as to supply carburizing fluid to the retort during the rotation thereof; said retort provided vvith a constricted vent.

15. A case-hardening ap aratus comprising a furnace havinga body and ends, and

' having a refractory lining for said body and ends, said lining forming a chamber in which the flames originate, a. metal/lic retort Wholly Within said chamber and having supporting extensions which rotrude through said ends, said furnace having kexterior sup orts upon which said extensions are revolu ly mounted, and a holder for carburizing fiuid connected to said retort so as to supply carburizing fluid thereto during the` rotation and heating of Athe retort; the latter provided with a constricted vent.

16. In combination, a closed retort formed of metal, means for causin the retort to heat quickly-and uniformly t roughout, and for maintaining an eventemperature of the heated retort, and means connected to the l retort at one end thereof for furnishing a, constant supply of carburizing-gas under pres- '.sure, and a constricted vent being provided 'at the other end of the retort.

17." In combination, a closed retort formed of metal, means for causing the retort to heat .quickly and uniformly throughout, and for maintaining an even` temperature of the heated retort-and means connected to the retort at one end vthereof for-furnishing a co'nstant supply. of carburizingas under pressure, and a constricted vent eing provided at the other end 'of the retort, and

power-driven mechanism for repeatedly a itating the articles in the retort during t ie carburizing operation.

18. In combination, a furnace having a flame-chamber, a metallic retort mounted Wholly Within the flame-chamber and having an extension which protrudes from the furnace, a cover for said retort, said cover applied to the retort Within the flame-chamber, releasable means exterior to the furnace and supported upon said extension, for retaining said cover, a holder for carburizin fluid connected to said retort and means or moving said retort so as to eect agitation of the ai'- ticles therein constantly during the heating thereof.

19. In combination a furnace having a name-chamber, a metallic retort mounted Wholly within the flame-chamber and having at its ends extensions Which protrudefrom the furnace, a cover for one end of said retort, said cover and the other end of said retort being both Within said flame-chamber, releasable means exterior to the furnace and supported'upon one of said extensions,for retaining said cover, a constricted vent being provided at the covered end of the retort, means upon said furnace revolubly supporting 'said extensions, power-driven means for effeotin slow revolution of the retort, and a holder or compressed carburizing-gas connected to the end of said retort opposite from said cover.

20, In combination, a furnace having a flame-chamber, a retort in the form of a barrel having ends, hollow supports extending from said ends and projecting from the furnace and revolubly mounted exteriorly of the furnace, one of said ends being in the form of a removable cover, and a removable cap closing the end of thev extension which is adjacent tosaid removable cover.

21. In combination, a furnace having a flame-chamber, a retort in the form of a b airel having ends, hollow supports extending from said ends and projecting from the fur.-

lnace and revolubly mounted exteriorly of the furnace, one of said ends being in the form yof a removable cover, and a removable cap closing thev end of the extension which is adj acentl to said removable cover; said removable cap being attached to said removable cover so that they may be removed together, and said cap being provided with a'packing. j

- 22. A case-hardening apparatus comprising a furnace having a single fire-chamber, a closed metallic retort Within said fire-chamber, a holder for carburizing-gas connected with said retort, a series of burners for mixed air and gas, said burners being all Within said burners being so disposed as to effect substaiitially uniform heating of the retort through- IIO 'fire-chamber and bein constructed to direct out its length; the retort being provided with a relatively minute vent, and also with a large normally closed opening distinct from said vent, through which the articles may be removed and meansv for effecting rotation of said retort. i 23. A caso-hardening apparatus comprismg a furnace, a closed metallic retort in the form of a barrel and wholly within the flamechamber of the furnace and supported by its ends, a holder for carburizing-gas connected with saidv retort, a row of oppositely-directed burners for air and fuel all in said flamechamber and disposed over said retort for the entire length of the latter and so disposed as to heat the retort with substantial evenness throughout its length, and a common exhaust in the bottom of said furnace for the .fialnes from said burners;

the retort being provided with a' relatively minute vent.

24. A case-hardening apparatus comprising a furnace having a refractory lining forming a single flame-chamber and provided with burners all Within said chamber, a metallic retort wholly Within said refractory lining, supporting means arranged exteriorly of said refractory lining, said retort being provided With means extending through said refractory lining to rest upon said supporting means, the retort being supported in such a manner as to permit of gradual permanent expansion of the retort independently of the furnace, a cover within said refractory lining for said retort, means extending to the exterior of the furnace for clamping said cover, .and a holder for iron-carburizing gas connected with said retort; the latter provided With a relatively minute vent.

. 25. A case-hardening apparatus comprisinigra furnace having a body and ends anda re actory lining for said body and ends and also A rovided with burners, a metallic retort Whol y Within said refractory lining, supporting means arranged at the ends ofsald furnace exteriorly 'of said refractory hmng, said retort being provided with hollowlextensions beyond its ends Which extend through said refractory lining, means being provided for engaging one end of the retort to prevent the latter from endWise displacement, and provision being made for accommodating end- Wise movement of the opposite end of the re.

tort due to the gradual permanent expansion of themetal, a holder for carburizing-gas, a connection extending from said gas-holder through one of the said extensions and communieating With-the interior of said retort, a cover at the other end of the retort, and cover-clamping means extending through the other exte'nsion to the exterior of the apparatus; the retort being provided with a relatively lninute vent.

26. A case-hardening apparatuscomprising a furnace, a metallic retort mounted therein, a holder for iron-carburizing gas outside of said furnace but connected With ysaid retort, and means for effecting movement of said retort to agitate its contentsduring the heating of the retort; .the latter-being provided with a minute veut.

27. A case-hardening apparatus comprising al furnace provided with rolls, a retort in the form of a barrel and confined wholly Within the {fame-chamber of said furnace and having hollow cylindrical extensions projecting to the exterior of the furnace and mounted for rotationupon said rolls, and a holder for iron-carburizing gas connected with said retort; the latterprovided with a relatively minute vent.

28. A case-hardening apparatus comprising a furnace, a metallic retort mounted therein and havin a large opening, a removable cover normal y closing said opening, means for effecting mechanical discharge of the incandescent articles from the retort through said opening, and a holder for iron-carburizing gas connected to said retort; the latter being provided With a relatively minute vent.

29. A case-hardening apparatus comprising a furnace provided with a flame-chamber and a retort, a cover for said retort, means for supplying iron-carburizing gas to and venting it from said retort, and means for tilting said furnace together with said retort to discharge the articles from said retort.

30. A case-hardening apparatus compris,- ing a furnace provided with a" flame-chamber and a retort, a cover for said retort, means for supplying gas to and venting it from said retort, and means for tilting said furnace together with said retort to discharge the articles from said retort, said furnace having a refractory lining and being provided With a chute through which said articles may discharge; said chute extending through said refractory lining.

31. A case-hardening apparatus comprising a furnace having a name-chamber and a movable metallic retort; said furnace being provided with supports for said retort, upon which supports the retort is so mounted in the flame-chamber that the flames may envelop the retort; and the latter being provided With a gas-supply and a vent; means for veffecting gentle movement of the retort; and means for e'ecting such a movement of the retort as will discharge the heated articles therefrom.

32. A case-hardening apparatus compris.- ing a furnaceprovided with a refractory lining and also with a supporting means; a revoluble metallic retort mounted upon said supporting means and thereby wholly supported Within said refractory lining so that a flame-space surrounds the retort; said retort being provided W-ith a gas-supply and a vent; means for effecting slow rotation of said retort; and means for tilting the retort..

33. Acase-hardening apparatus compris- ICO los

IZO

ing a furnace, a metallic retort, and means ing said retort; and means for effecting dissupporting said retort for rotation within charge of the hot articles from said retort 55 said furnace; said furnace being provided l through said exhaust-opening. f with a refractory lining and an outlet for l 39. A case-hardening apparatus compris-' products of combustion, and said retort lying ing a furnace having a refractory liningl and orizontally and being in such relation to said provided with burners, a metallic retort refractory lining and said outlet that the wholly within said refractory lining, bearing- 6o flames of the furnace are caused to circulate l rolls arranged exteriorly of said refractory around said retort in seeking the outlet; said lining, said retort bein provided with cylinretort having a gas-supply and a vent, and a drical ends extending through said refractory discharge from one end of said retort being lining to rest upon said rolls7 a cover within provided through said refractory lining; l said refractory lining for said retort, means 65 means being also provided for tilting said furextending to the exterior of the furnace for nace together with said retort. I clamping said cover, means for supplying gas 34. A case-hardening apparatus compristo and venting it from said retort, and means ing a furnace; a metallic retort lying therein; for tilting said furnace and retort; the lower said furnace being provided with supports cylindrical end of the latter being provided 7o upon which the opposite ends of the retort with an aperture for the discharge of articles are mounted for rotation, and the retort befrom the retort, and the furnace having a dising surrounded by a flame-space and having charge-opening beneath said aperture.

a cover, a gas-supply, and a vent; supports 40. A case-hardening apparatus comprisupon which one end of said furnace is pivoted7 ing a furnace having a refractory lining for its 7 5 and a screw for lifting the other end of said body and ends and also provided with burnfurnace. ers for burning mixed air and gas, means for 35. A case-hardening apparatus comprisregulating the supply of air and gas, a closed ing a furnace pivotally mounted at one end, horizontal cylindrical metallic retort wholly means at the other end for tilting the same, a within said refractory lining, bearing-rolls ar- 8o retort within said furnace, a cover for said reranged at the ends of said furnace exteriorly tort, a discharge-passage from said retort of said refractory lining, said retort being through the wall of the furnace, and means provided with hollow cylindrical extensions for supplying gas to and venting it from said at its ends' which extend through said reretort. fractory lining and whereby the retort is rev- 8 5 36. A case-hardening apparatus comprisolubly supported upon said rolls in such `ing a furnace, an inclined retort mounted a manner that one end of the retort is pretherein, a discharge-passage being provided vented from moving endwise while the other from the lower end of said retort and extendend thereof may move endwise to accommoing through the wall of the said furnace, and date the gradual permanent expansion of the 9o means for supplying ,iron-carburizing gas to -metal, a gas-supply extending through one of and venting it slowly from said retort. said extensions and communicating with the 37. A case-hardening apparatus comprisinterior of the retort, a cover at the other end ing a furnace pivoted at one end, a screw for of the retort, a discharge through the bottom elevatingthe other end of the furnace, a reof the furnace at the cover end of the retort, 95 tort within said furnace and means for supcover-clamping ineans'extending throughthe .plying gas to said retort. other extension to the exterior of the appara- 38. A case-hardening apparatus compristus, and means for tilting said furnace and remg afurnace havmgarefractorylining,arev tort; said furnace being provided with a oluble closed metallic retort mounted withpyrometer and with a sight-hole opposite the 100 in saidbfurnace and suirounded py a flamebody of said retort.

space, urners mounte over sai retort an exhaust-opening below the retort for ,the ADOLPH W' MACHLET' flames from'the burners, means for supplying Witnesses: f

gas to and venting it from said retort during PinLiP C. OSTERMAN,

the revolution; power-driven means for turn- GEO. L. HIRTZEL, J r. 

